a) Field of the Invention
The invention relates to a device for controlling the drive of mechanisms operating separately from one another, the control being adapted to different states of the mechanisms.
Such devices may be used, inter alia, for transfer devices for transferring objects between two locations, such as are required in semiconductor factories and by manufacturers for equipping such factories. The objects may be, for example, transport containers for material transport; the locations may be processing stations or depositing locations spatially removed from one another.
b) Description of the Related Art
In semiconductor factories, it is customary to transport the substrates to be processed in open or closed containers between different locations and different processing devices by transport devices specially designed for the purpose. In such cases, the handling of the containers during the required loading and unloading operations is to take place in an ergonomic way for the operating personnel. The latter is of special significance with the increasing size of substrates to be processed and the associated increase in size and weight of the containers.
Known simple transport carriages have a simple storage capability for the containers and require loading and unloading by the operating personnel.
Such a solution is important particularly whenever a transport system has to be used as an interim solution for an automatic system, because the containers to be transported exceed the ergonomically admissible limit. Specifically in the early and medium-term construction phase of semiconductor factories, manually operated transport systems are required in order to optimize fitting out and work procedures. However, such interim solutions usually rule out fully automatic systems with complicated and expensive electronics and sensor systems, for reasons of cost. This also applies to a mobile loading device according to U.S. Pat. No. 5,570,990 in the form of a carriage having a multi-member, swivelling transport arm, the members of which are pivotally connected to one another by joints and which is fastened to the upper end of a vertically adjustable shaft. The swivelling transport arm serves for transporting SMIF containers to a semiconductor processing installation and back to the carriage. For this purpose, the containers are seized by a gripper and set down at a depositing location of the semiconductor processing installation by a swivelling movement. The return transport takes place in the reverse way. Means for communication between the semiconductor processing installation and the carriage control monitor the procedures. While the operating personnel has to perform the movements with the transport arm in the x-y plane by turning the joints between the members of the transport arm without additional aids, a motor-driven auxiliary device is provided to relieve the work involved in the case of heavier items for the z movement of the transport arm.
It is disadvantageous that operating procedures separate from one another are required for different directions of the transport movement. This makes both the working sequence and the constructional design of the transporting device complicated and consequently costly.
As already described in U.S. patent application Ser. No. 08/977,588, it is often advantageous when using simple transport carriages to provide mechanisms in duplicate for the containers. If the transporting carriage is brought up to a processing device for loading and unloading, it is always possible to put into operation just the mechanism which is aligned with the processing device as the reference location. If one of the mechanisms is in operation, it is intended that the transport carriage be hindered from being able to move away from the reference location.
Both for reasons of expense and for reasons of user friendliness, it is desirable if just the actuation of a single drive element enables the operating personnel to meet these requirements.